Preparation of 3-amino-1,2,4-benzotriazine dioxide

1. A process for preparing 3-amino-1,2,4-benzotriazine 1,4-dioxide which comprises reacting benzofuroxan with cyanamide in the presence of an organic base in a non-aqueous medium at a temperature of about 20-25° C. followed by treatment with an organic acid.

2. A process according to claim 1 wherein the organic base is selected from the group consisting of DBU and DBN.

3. A process according to claim 2 wherein the organic base is DBU.

4. A process according to claim 3 wherein the organic acid is acetic acid.

5. A process according to claim 1 wherein benzofuroxan is reacted with cyanamide in a ratio of about 2 to 3 moles of cyanamide per mole of benzofuroxan in the presence of an organic base in a ratio of 2 to 3 moles of base per mole of benzofuroxan followed by treatment with an organic acid in a ratio of about 1 to 1.3 moles of acid per mole of base.

6. A process according to claim 5 wherein the base is selected from the group consisting of DBU and DBN.

7. A process according to claim 6 wherein the base is DBU.

8. A process according to claim 7 wherein the organic acid is acetic acid.

9. A process according to claim 8 which is carried out in the presence of a solvent selected from the group consisting of acetonitrile, acetone and isopropanol.

10. A process according to claim 9 wherein the solvent is acetonitrile.

11. A process according to claim 10 wherein benzofuroxan is reacted with cyanamide in a ratio of about 2 moles of cyanamide per mole of benzofuroxan in the presence of DBU in a ratio of about 2 moles of DBU per mole of benzofuroxan in acetonitrile at a temperature of about 20-25° C. followed by treatment with acetic acid in a ratio of about 1 mole of acetic acid per mole of DBU.

12. A process according to claim 11 which comprises the steps of:

a) reacting benzofuroxan with cyanamide in a ratio of about 2 moles of cyanamide per mole of benzofuroxan in the presence of DBU in a ratio of about 2 moles of DBU per mole of benzofuroxan in acetonitrile in a ratio of about 0.3:1 w/w acetonitrile/benzofuroxan at a temperature of about 20-25° C. for about 48 hours;

b) diluting the reaction mixture with acetonitrile in a ratio of about 5:1 w/w acetonitrile/benzofuroxan;

c) treating the reaction mixture with acetic acid in a ratio of about 1 mole of acetic acid per mole of DBU while maintaining the temperature below about 15° C.;

d) allowing the product to precipitate at about 5-10° C.; and

e) isolating the 3-amino-1,2,4-benzotriazine 1,4-dioxide from the reaction mixture.

13. A process according to claim 12 further comprising the steps of: dissolving the isolated 3-amino-1,2,4-benzotriazine 1,4-dioxide in aqueous methanesulfonic acid; filtering the solution;

adding the filtered solution to an aqueous solution of sodium acetate containing about 1 to 1.3 moles of sodium acetate per mole of methanesulfonic acid; and allowing the product to precipitate at about 10-25° C.